For full support in Home Assistant’s native Zigbee Home Automation integration (i.e. Home Assistant’s own built-in Zigbee gateway) developers might need to create some ZHA Device Handlers (a.k.a. zha-quirks) or ever make a few changes to the upstream zha and zigpy libraries for Shelly Zigbee devices to expose custom features and fully work properly out-of-the-box nativly via the ZHA integration if those devices use custom Zigbee clusters and attributes instead of fully following standard Zigbee. Without that they probably only expose basic attributes that are standard. For more information see more about that here where you can post feedback too:
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PS: For reference and more background information on what custom device handlers (zha-quirks) do for Zigbee devices with non-standard clusters and attributes in ZHA read this: